1. Field of the Invention
The present invention relates to a lithium rechargeable battery. More particularly, the present invention relates to a lithium rechargeable battery which may prevent an insulating case from moving inside a lithium rechargeable battery can.
2. Discussion of the Background
Small batteries with high capacities have become increasingly necessary as power sources in portable electronic appliances as portable electronic appliances are made lighter and more compact. Lithium rechargeable batteries are increasingly used in the industry because they have a high energy density per unit weight and an operating voltage of 3.6V, which is about three times larger than that of nickel-hydrogen or nickel-cadmium batteries.
Lithium rechargeable batteries create electric energy by oxidation and reduction reactions that occur during intercalation and deintercalation of lithium ions at the positive and negative electrodes. Materials that enable lithium ions to undergo reversible intercalation and deintercalation are used as the active materials of the positive and negative electrodes. An organic electrolyte or a polymer electrolyte may be used to fill the space between the positive and negative electrodes.
Lithium-containing metal oxide may be used as the positive electrode active material of the lithium rechargeable batteries. Examples of a lithium-containing metal oxide include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium manganese oxide (LiMnO2).
Lithium or lithium alloy was conventionally used as the negative electrode active material. Lithium has the drawback that the batteries tend to short-circuit and explode due to dendrite formation. To overcome this problem, lithium has been replaced by carbon-based materials, including amorphous and crystalline carbon. Lithium rechargeable batteries may be manufactured in various shapes including cylinders, squares, and pouches.
FIG. 1 is an exploded perspective view showing a conventional lithium rechargeable battery.
Referring to FIG. 1, a lithium rechargeable battery may be formed by placing an electrode assembly 12 including a first electrode 13, a second electrode 15, a separator 14, and an electrolyte into a can 10 and sealing an opening of the can 10 with a cap assembly 20.
The cap assembly 20 may include a cap plate 40, an insulation plate 50, a terminal plate 60, and an electrode terminal 30. The cap assembly 20 may be coupled to the opening of the can 10 and to a separate insulation case 70 that seals the can 10.
The cap plate 40 may be made from a metal plate having a size and a shape corresponding to the opening of the can 10. The cap plate 40 may have a terminal through-hole 41 of a predetermined size arranged at its center portion, into which the electrode terminal 30 may be inserted. A tubular gasket 35 may be coupled to the outer surface of the electrode terminal 30 to electrically insulate the electrode terminal 30 from the cap plate 40. In addition, an electrolyte injection hole 42 with a predetermined size may be arranged at one side of the cap plate 40 and a safety vent (not shown) may be arranged at another side of the cap plate 40. The safety vent may be integrally formed with the cap plate 40 by reducing the thickness of the cap plate 40. The cap assembly 20 may be coupled with the opening of the can 10. An electrolyte may be injected via the electrolyte injection hole 42, and the electrolyte injection hole 42 may then be sealed by a plug 43.
The electrode terminal 30 may be coupled with a second electrode tap 17 of the second electrode 15 or a first electrode tap 16 of the first electrode 13, so that the electrode terminal 30 may serve as a second electrode terminal or a first electrode terminal. Insulating tape 18 may be wound around portions of the first electrode tap 16 and the second electrode tap 17 drawn from the electrode assembly 12 to prevent a short circuit between the first electrode 13 and the second electrode 15. The first electrode 13 and the second electrode 15 may serve as a positive electrode and a negative electrode, respectively, or vice versa.
In a lithium rechargeable battery having the structure described above, the insulating case 70 may be arranged on the upper portion of the electrode assembly 12. However, the insulating case 70 may be easily moved if a physical impact is applied to the battery during a standard test, such as a drop test. If the insulating case 70 is moved, the first electrode tap 16 and the second electrode tap 17 extending upward through the insulating case 70 may also be moved, thereby causing a short circuit between the first electrode 13 and the second electrode 15.